Influence of rock mass fracture degree on the efficiency of its explosive destruction

Purpose. The purpose of the research is to establish the regularity of the influence of the degree of fracturing of the rock massif on the efficiency of its destruction by explosion of a borehole charge, namely, on the value of the maximum radius of the explosive crushing zone, by modeling the process of rock destruction in ANSYS AUTODYN. The methods. The complex research methodology was applied, which consists in the scientific analysis of existing research results on the fracture of fractured rock massifs, computer modeling of the process of explosive rock fracture in ANSYS AUTODYN, graphical and analytical establishment of dependencies of the influence of the fracture modulus of the massif on the maximum radius of the explosive fracture zone. Findings. According to the results of modeling in ANSYS AUTODYN the explosion of borehole charge Anemix 70 in granites of Pinyazevitsky deposit, the epiphyses of rock mass destruction with different value of strength reduction factor were obtained. The graphical dependence of the maximum radius of the fracture zone on the strength reduction factor, which can be described with a high level of reliability by a polynomial of the 3rd degree, has been constructed. It is established that the maximum radius of the fracture zone of an ideally strong massif is 2,15 times less than the radius of fracture obtained by explosion in a maximally weakened massif. Numerical values of maximum radii of fracture zones in granite massif at different indices of fracture modulus have been calculated and the corresponding graphical dependence, which is most accurately approximated by a polynomial of the 4th order, has been obtained. It is established that for monolithic massif the maximum value of radius in these conditions is 1,82 m, and for strongly fractured massif –3,0 m, i.e. it increases in 1,65 times. With further increase of fracture modulus the intensity of fractures increases more significantly. The originality. Graphical and analytical dependences of the maximum radius of the fracture zone at explosion of a cylindrical charge on the fracture modulus of the rock massif for certain mining and technological conditions have been obtained. Practical implementation. It is recommended to use the presented researches at designing of drilling and blasting operations in fractured rocky rock massifs for increase of degree of reliability of results of explosion.